The present invention relates to an industrial robot particularly suitable, for example, for painting or sealing the body of an automobile.
An industrial robot of typical conventional technology is shown in FIG. 6, with FIG. 7 showing a back view thereof as seen from the right of FIG. 6. With this industrial robot 1, a revolution portion 4 on a base 3 fixed to an installation surface 2 such as a floor is revolutionarily driven about a vertical revolutionary axis 5, a base end portion of a lower arm 7 is provided so as to be rotatably driven about a horizontal fore-and-aft axis 6 in the revolution portion 4, and an upper arm 9 is provided so as to be rotatably driven about a horizontal up-and-down axis 8 at a free end portion of the lower arm 7. A longitudinal axis 10 of the upper arm 9 lies within a plane passing through the revolutionary axis 5, and thus the upper arm 9 has no offset with respect to the revolutionary axis 5.
Problems associated with the use of the conventional industrial robot 1 shown in FIGS. 6 and 7 when it is working on an automobile body 11 are described below with reference to FIGS. 8A to 8C. As shown in the plan views of FIGS. 8A to 8C, the automobile body 11 is moved in the direction of an arrow 12 by a conveyor. The industrial robot 1 is provided to one side of the path of the automobile body 11 as it is moved by the conveyor, and it performs a painting or sealing operation thereon.
As shown in FIG. 8A, when the industrial robot 1 works on the interiors of an engine compartment 13 of the automobile body 11, having a hood 15 that covers the engine compartment 13 and is openable about a hinge 14 having a horizontal axis, a side edge 15a of the hood 15 or a side portion 13a of the engine compartment 13 can easily impede the upper arm 9 of the industrial robot 1. To prevent this interference, the upper arm 9 must enter the engine compartment 13 from the front thereof (the left in FIG. 8A), but if the installation position of the industrial robot 1 is moved in the direction of an arrow 17 to enable this entry, the automobile body 11 will interfere with the revolution portion 4 of the automobile body 11 as the automobile body 11 is conveyed in the direction of the arrow 12.
If the industrial robot 1 is moved in the direction of an arrow 18 and set thereat, a portion of the automobile body 11 indicated by 19 will be outside the operating range of the industrial robot 1. Therefore, it is difficult for a single unit of the conventional type of industrial robot 1 to work on the front portion of an automobile body 11, so there is no alternative but to position two industrial robots 1 symmetrically to the left and right (top and bottom in FIG. 8A) of the automobile body 11, and divide the work therebetween.
In order to work on a front floor 20 and a dashboard 21 within the passenger compartment when an industrial robot 1 is positioned to one side of the automobile body 11, as shown in FIG. 8B, a front door 24 is opened and the upper arm 9 of the industrial robot 1 is inserted through the opening 25 of the front door 24. When the industrial robot 1 is operating in a region 22 within the rear compartment, a door pillar 23 of the automobile body 11 may impede the upper arm 9 of the industrial robot 1 and thus make work impossible. A two-door automobile body 11 causes particular problems because there is no rear door opening and thus the industrial robot 1 cannot work in the rear compartment. Note that within the rear compartment of a four-door automobile body 11, one more industrial robot 1 for rear compartment work can be newly provided, and it works through the rear door opening.
When the industrial robot 1 works in the interiors of a trunk compartment 26, a luggage hatch 27, and a wheel arch 28, as shown in FIG. 8C, part of the work can be done by inserting the upper arm 9 of the industrial robot 1 with the luggage hatch 27 opened about a hinge 29 that has a horizontal axis, but, for the same reason as that illustrated in FIG. 8A, it is difficult for the industrial robot 1 to work on all the regions of the rear of the automobile body 11.
Furthermore, as shown in FIG. 7, a conventional robot has three motors 101, 102, 103 for three dimensionally driving a wrist provided at the free end portion of the upper arm at the end portion of the lower arm. However, as shown in FIG. 7, these three motors 101, 102, 103 are usually disposed laterally in a motor casing 100 provided at the base end portion of the upper arm. Therefore, it is difficult to decrease the robot size in horizontal direction resulting in occurrence of interference with work.
Still further, since a reduction gearbox for the up-and-down axis of a conventional robot is usually directly connected to a shaft of a drive motor, it is difficult for the industrial robot to reduce the size of the lower arm and the load of the motor for the fore-and-aft axis.